Clean up input handling in VulkanViewer

Sets up proper handling of characters and keycodes, and event modifiers.
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1865553005

Review URL: https://codereview.chromium.org/1865553005
diff --git a/tools/vulkan/VulkanTestContext.cpp b/tools/vulkan/VulkanTestContext.cpp
index 4a4c219..f9f037d 100644
--- a/tools/vulkan/VulkanTestContext.cpp
+++ b/tools/vulkan/VulkanTestContext.cpp
@@ -79,8 +79,7 @@
         return;
     }
 
-    // get this info from somewhere?
-    if (!this->createSwapchain(1024, 768)) {
+    if (!this->createSwapchain(-1, -1)) {
         this->destroyContext();
         return;
     }
@@ -152,7 +151,7 @@
         extent.height = height;
     }
 
-    // clamp width; to protect us from broken hints?
+    // clamp width; to protect us from broken hints
     if (extent.width < caps.minImageExtent.width) {
         extent.width = caps.minImageExtent.width;
     } else if (extent.width > caps.maxImageExtent.width) {